brainpopfandomcom-20200223-history
Fish/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are in their home. Tim is feeding his goldfish, who lives in a small aquarium. Moby pokes the side of the aquarium with his finger. The goldfish swims off and hides. TIM: He doesn't like it when you do that. Moby hands Tim a sheet of paper. Tim reads from a typed letter. TIM: Dear Tim and Moby, What makes a fish a fish? From, Uri. Fish are the largest group of vertebrates on Earth, with more than 29,000 known species. An image shows a large variety of fish swimming together in a group. TIM: Vertebrates are animals that have a backbone. The fish become silhouettes, with their backbones visible. TIM: Most fish are ectothermic, or cold-blooded; that means they can't generate their own body heat. They all use gills to get oxygen from the water. MOBY: Beep. TIM: Well, gills are membranes filled with tiny blood vessels. An image shows the head and gills of a fish. TIM: As blood flows through them, it picks up oxygen from the water passing by and releases carbon dioxide. Arrows show the route that water takes into a fish's mouth and out through its gills. TIM: Most fish have fins to help move them through the water, and thin, bony scales for protection. An image of a fish highlights the features Tim describes. TIM: And their streamlined bodies help them cut quickly through water. The fish swims away quickly. TIM: All fish fall into one of three categories: bony fish, cartilaginous fish, and agnathan, or jawless, fish. Images appear of each of the three types of fish Tim names. Each is labeled with its type. TIM: Bony fish are the biggest group of fish, making up about ninety-five percent of all the species. Like their name says, bony fish have skeletons made of bone. Moby stands in a lab coat, holding a clipboard and examining a wall covered with x-rays of fish. TIM: Most bony fish have a swim bladder. That's a sac of gas in their bodies that helps them control depth. When the sac inflates, the fish becomes more buoyant and rises in the water. When the bladder deflates, the fish becomes less buoyant and sinks. An animation shows a fish and the location of its swim bladder. The sac inflates as Tim describes, and the fish rises. Then the sac deflates as Tim describes, and the fish sinks. TIM: Cartilaginous fish include sharks, skates, and rays. They have skeletons made of cartilage, not bone. An image shows a shark, a skate, and a ray. MOBY: Beep. TIM: Cartilage is a rigid, soft tissue. Your upper ears are made mostly of cartilage. The brains of cartilaginous fish are ten times the size of other fishes', and they have actual tiny teeth called dermal teeth on their skin, making it very rough, like sandpaper. An image shows a shark. Text by the shark's head reads, 10x, to show how much larger its brain is. A close-up shows the exterior dermal teeth that Tim describes. TIM: Finally, there are the agnathans, the jawless fish, like the lamprey. Like the name says, jawless fish have no jaws, just a round sucker-mouth with teeth all along the inside. An image shows a lamprey and its sucker-mouth. TIM: Jawless fish are some of the oldest fish we know of. There are fossils of them that date back to 250 million years ago. MOBY: Beep. TIM: Yeah, I don't like to judge animals, but that mouth is kind of creepy. Fish are a huge source of protein for people. 25 percent of all of the animal protein consumed in the world comes from fish. Moby approaches the aquarium with a small net and a frying pan. TIM: Stop it. That's not food. That's Ewan. He's my pet. Moby goes closer to the aquarium. Tim grabs his arm. TIM: Aaah! Nope! Stop! Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts